The objectives of this proposal are two-fold. Firstly, we intend to acquire a dynamic description of the membrane components of normal erythrocytes, especially of spectrin-actin cytoskeleton and their responses to perturbations that are associated with shape changes that lead to the death of erythrocytes. Secondly, erythrocyte membrane proteins from hereditary spherocytosis (HS) patients will be studied in a similar manner in an attempt to reveal the molecular abnormality of HS. The major physical methods for this investigation are electron paramagnetic resonanace (EPR), saturation transfer (ST) EPR and spin label induced nuclear relaxation techniques.